@USBR needs to draw down Blue Mesa to meet winter target, water for Lake Powell

From The Grand Junction Daily Sentinel (Gary Harmon):

Blue Mesa this week was brimming at 99 percent full and it was far from alone among Colorado River Basin reservoirs.

Morrow Point and Crystal reservoirs below Blue Mesa on the Gunnison River were 96 percent and 90 percent full, respectively.

“It’s going to take a lot of work” to reduce Blue Mesa’s level to 70 percent of full, or 580,000 acre-feet of water, U.S. Bureau of Reclamation hydrologist Eric Knight said Thursday.

Typically, all three reservoirs are well depleted by this time of year to meet irrigation demand, as well as feeding more water into Lake Powell, the largest storage unit in the Upper Colorado River Basin.

This year, however, river managers learned late that there was more snow in the high Colorado mountains than they had believed when deciding how much water to release early on this spring, officials said during a regular update on management of the Aspinall unit.

Several factors contributed to the underestimation of snowpack, not least of them the warm March in the Colorado Rockies and the fact that some snow-monitoring gauges were covered with snow, incapable of providing accurate information, officials said.

Recent storms in the high country also have pumped more water into the reservoirs.

River managers have to balance the need to release more water out of the Aspinall unit with making sure that the Gunnison doesn’t overflow its banks in Delta.

At the same time, managers also have to get as much water as possible into Lake Powell, which can hold some 24 million acre-feet of water but which now holds about 15.2 million acre-feet.

The Bureau of Reclamation this year is to release 9 million acre-feet of water into Lake Mead.

Aspinall Unit operations update: 1150 CFS in Black Canyon

Fog-filled Black Canyon via the National Park Service

From email from Reclamation (Erik Knight):

The spring peak operation has officially concluded. Due to an issue with the power plant at Crystal Dam, the ramp down was forced to end prematurely. As of today releases are being made through the bypass gates at a rate of 2150 cfs. This has put flows in the Gunnison River through the Black Canyon around 1150 cfs. This release rate is expected to continue for the foreseeable future. Further adjustments to this release rate may be necessary to manage the remaining runoff coming into Blue Mesa Reservoir.

Aspinall Unit operations update: 4,500 cfs in Black Canyon — @USBR

Sunrise Black Canyon via Bob Berwyn

From email from Reclamation (Erik Knight):

The spring peak operation is nearing completion. Releases are currently being made to sustain half bankfull flow levels at the Whitewater gage, as well as to manage the forecasted runoff into Blue Mesa Reservoir. Releases from the Aspinall Unit have been around 5,500 cfs during the past week and that release rate will continue through Sunday, June 11th. Flows in the Gunnison River through the Black Canyon are currently around 4,500 cfs and can be expected to stay near this level through Sunday, June 11th. Starting on Monday, June 12th flows will begin to ramp down towards the summertime release level. This should result in flows in the Gunnison River through the Black Canyon around 900 cfs to 1,000 cfs once the ramp down is completed on Monday, June 19th.

Aspinall Unit operations update

Aspinall Unit dams

From email from Reclamation (Erik Knight):

The May 15th forecast for the April – July unregulated inflow volume to Blue Mesa Reservoir is 825,000 acre-feet. This is 122% of the 30 year average. Blue Mesa Reservoir current content is 681,000 acre-feet which is 82% of full. Current elevation is 7502.4 ft. Maximum content at Blue Mesa Reservoir is 829,500 acre-feet at an elevation of 7519.4 ft.

Based on the May 1st forecast, the Black Canyon Water Right peak flow target is listed below:

Black Canyon Water Right

The peak flow target is equal to 6,427 cfs for a duration of 24 hours.

The shoulder flow target is 831 cfs, for the period between May 1 and July 25.

The May 15th forecast of 825,000 af is now in the Average Wet category and the Aspinall Unit ROD flow targets have changed. Based on the May 15th forecast, the flow targets are listed below:

Aspinall Unit Operations ROD

The year type is currently classified as Average Wet.

The peak flow target is 14,040 cfs and the duration target at this flow is 2 days.

The half bank-full target is 8,070 cfs and the duration target at this flow is 20 days.

The spring peak operation has reached peak release level. The release increase made this morning, May 24th, should result in the first day of flows > 14,000 cfs at the Whitewater gage, arriving by the afternoon of May 25th. Today, flows in the Gunnison River through the Black Canyon have reached 11,500 cfs. The current rate of release is planned to continue through Sunday, May 28th. At this time it is projected that there is additional water that needs to be released from the Aspinall Unit to prevent overfilling at Blue Mesa Reservoir, therefore the peak release is continuing to meet more than the 2 day duration target.

@USBR Increases Releases from the Aspinall Unit to Meet Flow Targets on the Gunnison River

Black Canyon of the Gunnison

Here’s the release from the US Bureau of Reclamation (Justyn Liff/Erik Knight):

The Bureau of Reclamation began increasing releases from the Aspinall Unit, consisting of Blue Mesa, Morrow Point, and Crystal reservoirs on the Gunnison River, on May 14, 2017. The increased release will attempt to meet flow targets on the Gunnison River, designed to benefit endangered fish species downstream while continuing to meet the congressionally authorized purposes of the Aspinall Unit.

Flows in the Gunnison River through the Black Canyon will increase at a minimum of 500 cubic-feet-per-second a day resulting in flows through the canyon that may reach 12,000 cfs by approximately May 23. Flows will remain around 11,500 cfs to 12,000 cfs for 3-5 days before incrementally decreasing toward a range of 5,000 cfs to 5,500 cfs around May 29.

Aspinall unit operations update

Aspinall Unit

From email from Reclamation (Erik Knight):

The April 15th forecast for the April – July unregulated inflow volume to Blue Mesa Reservoir is 850,000 acre-feet. This is 126% of the 30 year average. Snowpack in the Upper Gunnison Basin is currently 124% of average. Blue Mesa Reservoir current content is 623,000 acre-feet which is 75% of full. Current elevation is 7495.3 ft. Maximum content at Blue Mesa Reservoir is 829,500 acre-feet at an elevation of 7519.4 ft.

Black Canyon Water Right

The peak flow and shoulder flow components of the Black Canyon Water Right will be determined by the May 1 forecast of the April – July unregulated inflow volume to Blue Mesa Reservoir. If the May 1 forecast is equal to the current forecast of 850,000 acre-feet of runoff volume, the peak flow target will be equal to 6,427 cfs for a duration of 24 hours. The shoulder flow target will be 831 cfs, for the period between May 1 and July 25. The point of measurement of flows to satisfy the Black Canyon Water Right is the Gunnison River below Gunnison Tunnel streamgage at the upstream boundary of Black Canyon of the Gunnison National Park.

Aspinall Unit Operations ROD

Pursuant to the Aspinall Unit Operations Record of Decision (ROD), the peak flow and duration flow targets in the lower Gunnison River, as measured at the Whitewater gage, will be determined by the forecast of the April – July unregulated inflow volume to Blue Mesa Reservoir and the hydrologic year type. At the time of the spring operation, if the forecast is equal to the current forecast of 850,000 acre-feet of runoff volume, the hydrologic year type will be set as Moderately Wet. Under a Moderately Wet year the peak flow target will be 14,350 cfs and the duration target at this flow will be 10 days. The duration target for the half bankfull flow of 8,070 cfs will be 40 days.

Projected Spring Operations

During spring operations, releases from the Aspinall Unit will be made in an attempt to match the peak flow of the North Fork of the Gunnison River to maximize the potential of meeting the desired peak at the Whitewater gage, while simultaneously meeting the Black Canyon Water Right peak flow amount. The magnitude of release necessary to meet the desired peak at the Whitewater gage will be dependent on the flow contribution from the North Fork of the Gunnison River and other tributaries downstream from the Aspinall Unit. Current projections for spring peak operations show that flows in the Gunnison River through the Black Canyon could be over 9,000 cfs for 10 days in order to achieve the desired peak flow and duration at Whitewater. If actual flows on the North Fork of the Gunnison River are less than currently projected, flows through the Black Canyon could be even higher. With this runoff forecast and corresponding downstream targets, Blue Mesa Reservoir is currently projected to fill to an elevation of around 7507 feet with an approximate peak content of 719,000 acre-feet.

Aspinall Unit operations update

Morrow Point Dam spilling June 2014 via USBR

From email from Reclamation (Erik Knight):

The April 1st forecast for the April – July unregulated inflow volume to Blue Mesa Reservoir is 930,000 acre-feet. This is 138% of the 30 year average. Snowpack in the Upper Gunnison Basin is currently 147% of average. Blue Mesa Reservoir current content is 582,000 acre-feet which is 70% of full. Current elevation is 7490.1 ft. Maximum content at Blue Mesa Reservoir is 829,500 acre-feet at an elevation of 7519.4 ft.

Black Canyon Water Right

The peak flow and shoulder flow components of the Black Canyon Water Right will be determined by the May 1 forecast of the April – July unregulated inflow volume to Blue Mesa Reservoir. If the May 1 forecast is equal to the current forecast of 930,000 acre-feet of runoff volume, the peak flow target will be equal to 6,575 cfs for a duration of 24 hours. The shoulder flow target will be 921 cfs, for the period between May 1 and July 25. The point of measurement of flows to satisfy the Black Canyon Water Right is the Gunnison River below Gunnison Tunnel streamgage at the upstream boundary of Black Canyon of the Gunnison National Park.

Aspinall Unit Operations ROD

Pursuant to the Aspinall Unit Operations Record of Decision (ROD), the peak flow and duration flow targets in the lower Gunnison River, as measured at the Whitewater gage, will be determined by the forecast of the April – July unregulated inflow volume to Blue Mesa Reservoir and the hydrologic year type. At the time of the spring operation, if the forecast is equal to the current forecast of 930,000 acre-feet of runoff volume, the hydrologic year type will be set as Moderately Wet. Under a Moderately Wet year the peak flow target will be 14,350 cfs and the duration target at this flow will be 10 days. The duration target for the half bankfull flow of 8,070 cfs will be 40 days.

Projected Spring Operations

During spring operations, releases from the Aspinall Unit will be made in an attempt to match the peak flow of the North Fork of the Gunnison River to maximize the potential of meeting the desired peak at the Whitewater gage, while simultaneously meeting the Black Canyon Water Right peak flow amount. The magnitude of release necessary to meet the desired peak at the Whitewater gage will be dependent on the flow contribution from the North Fork of the Gunnison River and other tributaries downstream from the Aspinall Unit. Current projections for spring peak operations show that flows in the Gunnison River through the Black Canyon could be over 8,500 cfs for 10 days in order to achieve the desired peak flow and duration at Whitewater. If actual flows on the North Fork of the Gunnison River are less than currently projected, flows through the Black Canyon could be even higher. With this runoff forecast and corresponding downstream targets, Blue Mesa Reservoir is currently projected to fill to an elevation of around 7518 feet with an approximate peak content of 816,000 acre-feet.